I had the same issue with my LG Q7+ in May 2019 and after reading other people's experiences I decided to wait and see if it would start working on its own. After almost 2 months, the vibration motor was still not working so I decided to take it to a phone repair shop in July. They replaced the motor and it started working again.
However, ever since I got it fixed, it has failed 4 times again but it would start working after a few minutes. Last night it stopped working again and it's been almost 24hrs with no vibration.
The first time I tried EVERYTHING including a hard reset but no luck. So I'm starting to think that it's a phone issue and not the motor itself. I plan on leaving it alone this time as I plan on upgrading soon. I've only had it for about a year and a half but I always have my phone on vibrate so this really is an issue for me. Plus, lately it's been a little slow too and again I've tried every possible solution to fix it but nothing.